The ecology of infections

Bacteria can influence each other's growth, also in the presence of antibiotics. This has been demonstrated by a study performed in Wageningen examining bacteria that cause bladder infections in the elderly. Bacteria often form a miniature ecosystem. They respond to each other and to external influences such as food or antibiotics. Insight into the interactions between bacteria is of fundamental interest and of particular interest for medical practice, for instance in cases of bladder infections. In the elderly, bladder infections are often caused by not just one but several types of bacteria at the same time – polymicrobial infections – and the different bacteria also have different levels of resistance to antibiotics.

Ecosystem

Biologist Marjon de Vos of Wageningen University & Research is performing research into the role of the environment (ecology) in the development (evolution) of bacteria. ‘Bacteria living alongside each other, for instance in the intestines or urinary tract, form their own ecosystem. A polymicrobial infection can also be viewed as a small-scale ecosystem. It is starting to become clearer that interactions between bacteria are important for the composition and properties of such an ecosystem. Infections and the development of antibiotics resistance should therefore be examined in this light.’

Laboratory test

By means of laboratory experiments with the bacteria that caused urinary tract infections in the elderly, De Vos demonstrated the existence of competition and cooperation within the bacterial ecosystem. In one-to-one relationships between the culprits, she also discovered that bacteria can protect each other against antibiotics, or alternatively make each other more susceptible. ‘A bacterium appears to leave substances behind that make other bacteria more or less susceptible to an antibiotic,’ explains De Vos.

We saw interactions between bacteria that are involved in urinary tract infections.

Marjon de Vos. Researcher at the Laboratory of Genetics, Wageningen University & Research.

Application

The translation of these laboratory results into practice promotes new insights into the development of antibiotics resistance, and could therefore also contribute to the question of how is it possible that bladder infections in the elderly are sometimes not immediately cured with a course of antibiotics, or that the infections return. ‘Antibiotics are generally tailored to the most common type of bacteria. However, it appears worthwhile to look beyond the most common bacteria, as the microbial ecosystem can determine the survival of bacteria.’

Contribution to health

Insight into the coexistence of polymicrobial infections could therefore contribute to knowledge about how such an ecosystem can be disturbed. In turn, this contributes to knowledge on possible new ways of combating infection, according to De Vos. ‘Everything points to a necessity to view bacterial infections and antibiotics resistance from an ecological and evolutionary perspective.’

About Marjon de Vos

At Wageningen University & Research, Marjon de Vos performs quantitative system biological in-vitro experiments with bacteria from polymicrobial infections in order to address and answer ecological and evolutionary questions. To this end, she has been granted a Veni grant by the Netherlands Organization for Scientific Research (NWO).